Forums :: Resources :: Features :: Photo Gallery :: Vintage Radio Shows :: Archives :: Books
Support This Site: Contributors :: Advertise


It is currently Apr Wed 24, 2019 4:53 am


All times are UTC [ DST ]





Post New Topic Post Reply  [ 9 posts ] 
Author Message
 Post subject: Schematic Conventions for Capacitors
PostPosted: Apr Sun 14, 2019 7:28 pm 
Member

Joined: Nov Wed 30, 2016 7:35 pm
Posts: 3776
Location: Sunbury, Ohio 43074
To continue a topic from a test equipment question, but pertaining to parts rather than equipment:

Does anyone know if there ever was a "conventional" way to draw a capacitor? As noted in the Eico thread, electrolytics were "usually" shown with the curved side as the negative, with a + by the straight side. But this was reversed in schematics enough times that I wonder if there ever was any attempt to standardize on it.

This also pertains to the outer foil in non electrolytic caps as well. But I really never paid too much attention to which was "conventional" ... was the straight side, or the curved side, "supposed" to be the outer foil? Or, more likely, was it just up to the draftsman or the manufacturer of the equipment to decide on a case by case basis?

_________________
Preserving the history of electronics, one boat anchor at a time! :)
www.bbtvtestequipment.com


Top
 Profile  
 
 Post subject: Re: Schematic Conventions for Capacitors
PostPosted: Apr Sun 14, 2019 9:36 pm 
Member
User avatar

Joined: Nov Sat 07, 2009 11:37 pm
Posts: 2050
Location: Sayreville, NJ 08872
There are "European" standards and there are "U.S." standards.
Pick your needs:
https://www.google.com/search?q=capacit ... 83&bih=732

_________________
Pete, WA2CWA - "A cluttered desk is a sign of genius"
http://www.classicradiomanuals.com


Top
 Profile  
 
 Post subject: Re: Schematic Conventions for Capacitors
PostPosted: Apr Sun 14, 2019 11:05 pm 
Member
User avatar

Joined: Oct Sun 15, 2006 12:57 pm
Posts: 6283
Location: Liberty, Missouri
Cap symbols have been pretty standard for at least the last 75 years or so, and I think there were EIA standards starting in the early 30s.

As for orientation, I suspect those may have simply been oversights.

_________________
Pics, Bold & underlined text, are usually links.

https://mikeharrison.smugmug.com/

Mike


Top
 Profile  
 
 Post subject: Re: Schematic Conventions for Capacitors
PostPosted: Apr Sun 14, 2019 11:26 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 34118
Location: Maryland 20709, USA
I suggest determining polarity based on the rectifier cathode.

That never lies.

If you expect schematics to always be 100% correct, you're in for a major attitude shift.

One common issue often encountered is the cap's positive grounded to chassis. This happens when the cap's negative goes to the HV winding CT and there are dropping resistances.

the HV winding CT is always the most negative point in the power supply.

- Leigh

_________________
73 de W3NLB
http://www.AtwaterKent.info
Click "Grebe Stuff" for Synchrophase info


Top
 Profile  
 
 Post subject: Re: Schematic Conventions for Capacitors
PostPosted: Apr Mon 15, 2019 12:09 am 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 7504
Location: Minneapolis, MN USA
Barry,
Do you like banging your head ? :D

The are numerous conventions for drawing caps. There will never be a unified single standard agreement among thousands of electronic device manufactures as to which one to use on "their" schematics, regardless of which generation they come from. You can generalize and say the curved side, or the U shape (Philco) usually represents this or that polarity, but you or the schematic you find will be wrong too often to be reliable.

The reality is that you must understand what polarity the circuit location is established as. For vintage radios, there are some rules of thumb that help greatly when making the decision. You only need match one rule of thumb in the list to properly orient the cap.

Most cap replacement polarity decisions are straight forward due to some simple rules.
1-the center tap of the power transformer is always the most negative point in the radio power supply.
2-the cathode of the rectifier is always the most positive point.
3-if a cap lead goes to the plate of the output tube, it is positive.


Top
 Profile  
 
 Post subject: Re: Schematic Conventions for Capacitors
PostPosted: Apr Mon 15, 2019 3:35 am 
Member

Joined: Nov Wed 30, 2016 7:35 pm
Posts: 3776
Location: Sunbury, Ohio 43074
Quote:
Barry, Do you like banging your head ? :D


Well, if I don't do it, someone else will ;-)

_________________
Preserving the history of electronics, one boat anchor at a time! :)
www.bbtvtestequipment.com


Top
 Profile  
 
 Post subject: Re: Schematic Conventions for Capacitors
PostPosted: Apr Mon 15, 2019 11:23 am 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 5129
Location: Montvale NJ, 07645
Barry H Bennett wrote:

Does anyone know if there ever was a "conventional" way to draw a capacitor? As noted in the Eico thread, electrolytics were "usually" shown with the curved side as the negative, with a + by the straight side. But this was reversed in schematics enough times that I wonder if there ever was any attempt to standardize on it.


I expect to see the straight line as the positive side with a + symbol there also. Not sure I have ever seen the positive side indicated as the curved side, but I guess it has happened. Maybe I will take a look at the Eico thread to see what you are talking about.

I don't think I have ever seen anything special on a schematic indicating foil side, but it is very straight forward to determine the lower potential side for foil, so they probably never saw a need to indicate it.


Top
 Profile  
 
 Post subject: Re: Schematic Conventions for Capacitors
PostPosted: Apr Mon 15, 2019 9:30 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 4818
Location: Perrysburg, OH, U.S.A.
Getting back to symbols rather than circuit connections, these are the symbols I've standardized on in my schematics:
Attachment:
Capacitor Symbols.jpg
Capacitor Symbols.jpg [ 40.23 KiB | Viewed 97 times ]

John

_________________
“Never attribute to malice that which can be adequately explained by stupidity.”
― R. A. Heinlein


Top
 Profile  
 
 Post subject: Re: Schematic Conventions for Capacitors
PostPosted: Apr Mon 15, 2019 10:30 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 5129
Location: Montvale NJ, 07645
I agree with those John. I use the same on my schematics.


Top
 Profile  
 
Post New Topic Post Reply  [ 9 posts ] 

All times are UTC [ DST ]


Who is online

Users browsing this forum: Exabot [Bot], Usually Lurking and 4 guests



Search for:
Jump to:  




























Privacy Policy :: Powered by phpBB